It has been reported that the number of deaths due to lung cancer is the largest as 19% of all cancer deaths, and 1.8 million new cases per year worldwide are newly affected (GLOBOCAN, 2012). In non-small cell lung cancer (NSCLC) which is set to occupy nearly 80% of lung cancer, (American Cancer Society. Cancer Facts and Figures, 2016), although surgical therapy has been considered until a certain stage, and after that stage, chemotherapy or radiotherapy is used as a main treatment without having surgical adaptation. Based on cell morphology, adenocarcinoma and squamous cell carcinoma are classified as the most common type of NSCLC. The clinical course of these tumors is similar, but adenocarcinoma is characterized by the peripheral localization of the lungs.
RAS protein is a small molecule guanosine triphosphate (GTP) binding protein of approximately 21 kDa consisting of 188 to 189 amino acids, and there are four main proteins (KRAS (KRAS4A and KRAS4B), NRAS, HRAS) generated from three genes such as KRAS gene, NRAS gene, and HRAS gene. RAS protein has two types of a GTP binding type which is an active form and a guanosine diphosphate (GDP) binding type which is an inactive form. The RAS protein is activated by exchanging GDP for GTP by ligand stimulation to cell membrane receptor such as EGFR. The active form RAS binds to about 20 kinds of effector proteins such as RAF, PI3K, and RALGDS, and activates a signal cascade on the downstream. On the other hand, active form RAS becomes inactive by converting GTP to GDP by endogenous GTP hydrolysis (GTPase) activity. This GTPase activity is enhanced by GAP (GTPase activating protein). From this, RAS plays an important “molecular switch” function in intracellular signaling pathway such as EGFR and plays an important role in progress of cell growth, proliferation, and blood vessel formation (Nature rev. cancer, 11, 761, 2011, Nature rev. drug discov., 13, 828, 2014, Nature rev. drug discov., 15, 771, 2016).
When amino acid substitution occurs due to mutation of RAS gene, it is considered that the proportion of the active form increases due to a decrease in endogenous GTPase activity or a decrease in affinity for GAP. It is considered that excessive signal transmission resulting from this causes carcinogenesis and cancer growth proliferation. In the lung cancer, the mutation of the RAS gene was observed in 32% of pulmonary adenocarcinoma. It has been reported that the breakdown of the mutation frequency is 96% of the KRAS gene, 3% of the NRAS gene, and 1% of the HRAS gene, and there are many point mutations of KRAS exon 2 (codon 12, codon 13). In particular, the G12C mutation in which glycine at codon 12 is substituted with cysteine is a frequent mutation in the KRAS gene and occupies the highest proportion as 44% of the KRAS gene mutation observed in pulmonary adenocarcinoma (Nature rev. drug discov., 13, 828, 2014).
In the creation of a KRAS inhibitor, it is ideal to selectively inhibit a function of KRAS mutant protein. On the other hand, since a resulting mutation site is a distal from an effector binding site, obtaining a compound having selectivity in an inhibitory activity of a mutant type and a wild type is generally considered to be difficult (Bioorg. Med. Chem. Lett., 22, 5766, 2012). In recent years, a compound which is irreversibly bonded to G12C mutation KRAS (Nature, 503, 548, 2013, Angew. Chem., Int. Ed. Engl., 53, 199, 2014, Cancer Discov., 6, 316, 2016) by forming a covalent bond with respect to a mutation cysteine has been reported along with the existence of an allosteric pocket in the vicinity of a region called switch II being shown (Nature, 503, 548, 2013) against the G12C mutation KRAS. A G12C mutation KRAS selective inhibitor inhibits conversion from the inactive form to the active form by covalently binding to the G12C mutation KRAS and induces cancer cell death by blocking the downstream signal. Accordingly, a compound with this mechanism of action has been reported to be useful for a treatment of KRAS G12C mutation positive lung cancer.
It has been reported that compounds represented by Formula (A) and Formula (B) have binding capacity for the G12C mutation KRAS (Patent Documents 1, 2, and 3), and Patent Document 2 discloses a compound of Example 1-59 (hereinafter, also referred to as Compound C).
(The meanings of the symbols in the formulae refer to Patent Documents)
